Tissue engineering of bone: The role of osteoblasts and osteoclasts

A problem presented at the UK MMSG Strathclyde 2004.

Presented by:
Zhidao Xia (Botnar Research Centre, Nuffield Department of Orthopaedic Surgery, University of Oxford)
CJW Breward, Z Xia

Problem Description

Osteoblasts and osteoclasts play important roles in bone metabolism. Osteoblasts produce bone matrix and result in increases of bone mass. Osteoclasts resorb bone matrix and result in osteocyte (the terminal stage of osteoblasts) apoptosis and decreases of bone mass. In normal condition, the resorption will be followed by new bone formation, to keep the balance of bone mass to suit the change of bone mechanical environment and to repair micro-damage.

Current tissue engineering research is mainly targeting bone forming cells, namely osteogenic stem cell and progenitors which give rise to osteoblasts. These cells have great potential to form mineralised tissue both in vitro and in vivo. However, as only bone-forming cells are used, it is a static bone modelling system. Once cells are in contact with each other, the cell growth will be ceased and it can not form a self-renewal dynamic system.

At the Botnar Research Centre in Oxford, we are trying to understand the dynamic behaviour between the two cell types using an in vitro culture system. However, the major difficulty we are facing is to have a mathematical tool to quantify the two cell populations and to predict cell growth patterns in this dynamic system.

The study group was asked to formulate models to predict how the cells proliferate over time, and to help answer the following questions:

  1. How do osteoblasts and osteoclasts maintain a dynamic cell balance to ensure coherent structure of the formed tissue?
  2. What role does cell migration versus cell proliferation play in maintaining this balance?
  3. What is the optimum method for removing cell waste products from the tissue structure, e.g. diffusion?

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